When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Check the speed sensor, and the wires leading to it, on the top of the rear axle pumpkin. You will have to remove the sensor and clean it, and may have to replace it. Use a Motorcraft part if you replace it. The ECM uses the speed sensor to tell the auto tranny when to shift.